In heat pump applications, the switchover from the heating to the cooling mode, and vice versa, reverses the direction of flow for the refrigerant such that the coils serving as the condenser and evaporator, respectively, reverse functions. Where the compressor operates in a single direction, the change in the direction of the flow is generally achieved through a valving arrangement located externally of the compressor. If the compressor itself is reversible, it can be selectively run in either direction to, thereby, achieve the desired direction of flow. The simple reversal of the motor is not, in and of itself, sufficient to produce a compressor with satisfactory performance in both directions. This unequal performance in both directions is due to the switching between high and low side compressor operation, the changes in the cooling requirements and the cooling flow, the reversal of porting function and direction of opening/closing, etc.